1. Field of the Invention
The present invention relates to a conductive paste used for forming an electrode of a ceramic electronic component and to a ceramic electronic component.
2. Description of the Related Art
Ceramic electronic components are provided with sintered ceramic body made of ceramic materials, for example, dielectrics, semiconductors, and piezoelectric materials. Conductive pastes have been frequently used as materials for electrodes and wirings accompanying these ceramic electronic components.
In the conductive paste used for forming an electrode of a ceramic electronic component, a glass powder is added in some cases. The addition of the glass powder to the conductive paste generally has the effect, for example, of softening and fluidizing during the firing of an electrode so as to accelerate sintering of the conductive powder, of improving adhesive strength of a thick film electrode, and furthermore, of filling in pores generated at the interface between the thick film electrode and the sintered ceramic body so as to prevent capacitance from decreasing in the case in which the electronic component is a ceramic capacitor.
As conventional conductive pastes used for forming electrodes of ceramic electronic components, Pb glasses have been frequently used. In recent years, however, in consideration of environmental problems, it is necessary to substitute these with non-Pb glasses.
Ceramic electronic components, in particular, medium and high voltage ceramic capacitors with electrodes formed using conductive pastes containing conventional non-Pb glass, for example, Bi glass, have problems in that the heat-generating temperatures of sintered ceramic body are higher than those of medium and high voltage ceramic capacitors with electrodes formed using conventional conductive pastes containing Pb glass. This is believed to be due to the Bi in the glass diffusing into the ceramic and being reduced so as to become a semiconductor while being applied with a high voltage and high frequencies, and therefore, tan xcex4 of the sintered ceramic body increases.
The present invention was made to solve the aforementioned problems. Accordingly, objects of the present invention are to provide a conductive paste containing no Pb glass and suppressing heat generation in a sintered ceramic body, and to provide an electronic component with thick film electrodes formed thereof.
So as to achieve the aforementioned objects, a conductive paste according to the present invention is a conductive paste containing substantially no Pb and used for forming a thick film electrode of a ceramic electronic component, comprising a conductive powder containing Ag; a glass powder containing Bi, B and at least one alkaline earth metal selected from the group consisting of Ca, Sr, and Ba; and a vehicle, wherein when the alkaline earth metal, bismuth, and boron are expressed as oxides MO, Bi2O3, and B2O3, respectively, the content of the oxides are in the following ranges on a basis of % by mole relative to 100% by mole of the glass composition, 30 less than MOxe2x89xa640; 10xe2x89xa6Bi2O3xe2x89xa660; and 10xe2x89xa6B2O3xe2x89xa660, where M indicates the alkaline earth metal.
The content of the aforementioned glass powder is preferably about 1 to 15% by volume relative to 100% by volume of the aforementioned conductive powder.
A ceramic electronic component according to the present invention comprises a sintered ceramic body and thick film electrodes formed on two end faces of the sintered ceramic body using a conductive paste according to the present invention.